Modulation and Filter

Modulation and Filter

Patch-level FM, PWM, Ring Modulation, and Filter act after FWG has constructed the endpoint's base table. START and END own these settings independently, so a Morph can also move between different modulation/filter states.

In Playground or either Morph endpoint, open the endpoint's Modulation and Filter panels. These are downstream patch controls, separate from the three controls inside the selected Core Generator.

Generator FM is not the same as oscillator FM

The FM Generator Family uses frequency-modulation ideas while constructing source tables.

The patch-level FM control modulates oscillator playback during audition/render. It works with any Generator Family—including the FM family itself.

FM

🎹 Patch FM changes oscillator phase advance over time. Small depths can behave like vibrato; stronger settings create harmonic or inharmonic sidebands, metallic movement, and eventually unstable/noisy pitch behaviour.

The main controls are FM amount, FM pitch range, and the modulation source/rate settings exposed by the patch. Pitch Range is dormant while FM amount is zero; the value remains stored for later use.

PWM

🎹 PWM applies pulse-width-style phase movement to the oscillator path. Depending on the source table it can produce hollow motion, moving edge density, comb-like changes, or strong changes around discontinuities.

Do not expect every source to behave like classic analogue PWM. Audition PWM after choosing the generator, tap routing, and Wavetable Type.

Ring Modulation

🎹 Ring Mod multiplies the completed oscillator signal by a modulation signal. Use it for metallic sidebands, low-rate tremolo-like motion, non-harmonic textures, or aggressive digital movement.

Because the operation is bipolar multiplication rather than a simple volume fade, strong Ring Mod can change apparent pitch as well as timbre.

Filter

The patch filter is downstream of the generated oscillator/modulation path. Use it to remove or emphasise spectral regions before later Morph/export processing.

The main controls are filter type, Cutoff, and Resonance.

FWG accepts expert Cutoff values below the ordinary slider's 20 Hz floor through numeric entry/import. The slider remains optimised for 20 Hz–20 kHz.

When Filter is Off, Cutoff and Resonance remain stored but have no audible effect until a filter is enabled again.

A practical order for sound design

🎹 When learning a patch, work in layers:

1. make the generator/taps/Wavetable Type useful first;
2. shape Source / Result Windows if you want to change which table region becomes the cycle;
3. add FM/PWM/Ring one at a time;
4. add filtering after you understand the unfiltered modulation;
5. then introduce START→END Morph movement.

This makes it much easier to identify where a useful—or unwanted—quality came from.

Modulation inside Morph

START and END own separate modulation/filter settings.

Interpolating Morph modes can move current values between endpoints. Crossfade/fixed-branch modes may retain more independent endpoint identities.

START-mod-END is a separate relationship: one endpoint becomes an external modulation source for the other. See Morph Render Modes.

Bulk Random and Explorer

Bulk Random can randomise modulation/filter settings according to its selected pool. Explorer lets you hold those values fixed or vary them around the current patch.

If modulation is already near a useful boundary, use small Explorer variation first; large FM/filter changes can overwhelm subtler generator differences.

Cleanup caution

⚠️ Strong modulation or resonance can create large peaks or DC/level changes. Final DC removal and normalisation are separate render choices.

Normalisation does not make differently modulated patches perceptually equivalent. It only applies the selected final level policy.

Technical note: dormant controls

🔧 FWG preserves complete editable patch state even when a control is dormant. Changing Cutoff/Resonance while Filter is Off does not change current audio, but those stored values matter if a filter is later enabled or an interpolating Morph makes them active.

The renderer/cache compares effective dependencies so dormant changes need not force duplicate work. That is an optimisation, not a different patch-storage rule.

Related pages

• Signal Path and Core Concepts
• START→END Morph
• Morph Render Modes
• Render and Export Settings

Filter Cutoff interpolation in Morph

🔧 Filter Cutoff is a frequency quantity represented on a logarithmic domain. START→END Morph therefore interpolates Cutoff by frequency ratio, not linear Hz distance:

cutoff(t) = START × (END / START)^t

A 20 Hz → 20,000 Hz Morph passes through the geometric-mean midpoint, about 632.456 Hz. This matches the Cutoff control and Explorer's cents/ratio variation model.